Multidrug-resistant Human Lung Cancer Research Articles

Indole Curcumin Reverses Multidrug Resistance by Reducing the Expression of ABCB1 and COX2 in Induced Multidrug Resistant Human Lung Cancer Cells

Background: Drug resistance by the cancer cells towards current chemotherapeutic approaches poses a great challenge. In the present study, an indole analogue of a well-known plant derived anticancer molecule, curcumin, was tested for its Multidrug Resistance (MDR) reversing potential in induced multi drug resistant A549 cell line. Materials and Methods: Human lung cancer cell line A549 was made Multidrug Resistant (MDR) by prolonged treatment with low dosage of Docetaxel, an established anticancer drug. The MDR induction was confirmed by morphological evidence, Hoechst 33342 staining, MTT assay, Rhodamine123 staining and RT-PCR of ABCB1 gene. Protein expression studies were carried out using western blotting technique Results and Discussions: The induced MDR A549 cells exhibited significant increase in the gene expression of ABCB1 gene at the transcriptional level. Retention and efflux studies with Pglycoprotein (P-gp) substrate Rh123 indicated that indole curcumin inhibited P-gp mediated efflux of Rhodamine. Furthermore, treatment of MDR A549 cells with indole curcumin showed downregulation of gene expression of ABCB1 and COX 2. This was also confirmed from the decreased protein expression of COX 2. Conclusion: The results of the present study indicate that indole curcumin reverses multi drug resistance by downregulating the expression of ABCB1 and COX 2 genes. Thus, indole curcumin may act as a potent modulator for ABCB1 and COX 2 mediated MDR in lung cancer.

Caged-xanthone from Cratoxylum formosum ssp. pruniflorum inhibits malignant cancer phenotypes in multidrug-resistant human A549 lung cancer cells through down-regulation of NF-κB.

Our recent study reported that multidrug-resistant (MDR) human A549 lung cancer cells (A549RT-eto) with the elevated expression of NF-κB showed epithelial-mesenchymal transition (EMT), increasing spheroid formation and elevating the expression levels of stemness-related factors, including Oct4, Nanog, Sox2, Bmi1, and Klf4. Therefore, when new therapeutic agents targeting these malignant cancer cells were explored, we found that caged-xanthone (CX) isolated from the roots of Cratoxylum formosum ssp. pruniflorum diminished the expression of NF-κB, P-glycoprotein (P-gp) protein levels, cell migration and invasion, and sphere-forming ability of A549RT-eto cells. To address the role of NF-κB in these malignant cancer features, we treated A549RT-eto cells with NF-κB siRNAs in the present work. We found that the knockdown of NF-κB inhibited EMT and sphere formation. Furthermore, co-treatment with CX and NF-κB siRNA accelerated the death of apoptotic cells through the decrease of P-gp protein levels. These results suggest that NF-κB was involved in malignant cancer phenotypes and MDR in A549RT-eto cells. Taken together, our findings suggest that CX can be a potential therapeutic agent for the treatment of malignant tumor cells.

Structure activity relationship of annonaceous acetogenins against multidrug resistant human lung cancer cell line A549/Taxol in vitro

10 kinds of annonaceous acetogenins were selected for antitumor activity testing against human lung cancer cell line A549/Taxol and the structure activity relationship was analyzed.MTT assay was used to detect the inhibitory activities of 10 kinds of annonaceous acetogenins and positive drugs against A549/Taxol cells, respectively uvariamicin-Ⅲ(1), uvariamicin-Ⅱ(2), annosquacin D(3), desacetyluvaricin(4), annosquatin A(5), squamostatin D(6), bullatacin(7), squamocin(8), motrilin(9), annosquatin B(10), verapamil and cisplatin. Annonaceous acetogenins showed significant inhibitory activities against A549/Taxol cells, and were more potent than the positive drug verapamil and cisplatin.The more carbon atoms between the tetrahydrofuran ring and the lactone ring of annonaceous acetogenins exhibited more potency.Besides,ACGs with two substituted hydroxyl showed more potency than the compounds with three substituted hydroxyl in the bis-adjacent-THF ACGs. Furthermore, ACGs with three substituted hydroxyl showed more potency than the compounds with four substituted hydroxyl among the no bis-adjacent-THF ACGs.

Structure–activity relationships of diverse ACGs against multidrug resistant human lung cancer cell line A549/Taxol

Fifteen annonaceous acetogenins (ACGs) with different stereochemical structures and configuration, representing three main classes of bis-adjacent-tetrahydrofuran (THF), bis-nonadjacent-THF, and mono-THF ACGs, were selected to tested for their inhibition activity on A549/Taxol cell line, which is multidrug resistant (MDR). The present study showed that some tested compounds showed significant activity toward A549/Taxol cells, and were more potent than the positive control Verapamil. For example, squamostatin-D (14) (IC50 value=16.19μM) was 7.8 times more active than Verapamil (IC50 value=127.09μM). Those ACGs with more carbons between the THF ring and the γ-unsaturated lactone were more potent. Moreover, ACGs with stereochemical arrangement of erythro were more active than those of threo, the compounds with THF ring configuration of cis seemed to be superior to those of trans. However, if all other structural features were identical, the ACGs with more hydroxyls on the aliphatic chain were not more potent towards A549/Taxol, which was not in accordance with previous studies. Furthermore, bis-nonadjacent-THF ACGs whose molecular weight is 622, with three hydroxyl groups located at carbon 16, 19, 24 and stereochemical arrangement of erythro possibly produced notable cytotoxicity. Based on the above conclusions, we proposed a compound model that may be a promising anti-MDR cancer candidate drug in the future clinical trial.

Dual Inhibition of Met Kinase and Angiogenesis to Overcome HGF-Induced EGFR-TKI Resistance in EGFR Mutant Lung Cancer

Acquired resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) is a serious problem in the management of EGFR mutant lung cancer. We recently reported that hepatocyte growth factor (HGF) induces resistance to EGFR-TKIs by activating the Met/PI3K pathway. HGF is also known to induce angiogenesis in cooperation with vascular endothelial growth factor (VEGF), which is an important therapeutic target in lung cancer. Therefore, we hypothesized that dual inhibition of HGF and VEGF may be therapeutically useful for controlling HGF-induced EGFR-TKI-resistant lung cancer. We found that a dual Met/VEGF receptor 2 kinase inhibitor, E7050, circumvented HGF-induced EGFR-TKI resistance in EGFR mutant lung cancer cell lines by inhibiting the Met/Gab1/PI3K/Akt pathway in vitro. HGF stimulated VEGF production by activation of the Met/Gab1 signaling pathway in EGFR mutant lung cancer cell lines, and E7050 showed an inhibitory effect. In a xenograft model, tumors produced by HGF-transfected Ma-1 (Ma-1/HGF) cells were more angiogenic than vector control tumors and showed resistance to gefitinib. E7050 alone inhibited angiogenesis and retarded growth of Ma-1/HGF tumors. E7050 combined with gefitinib induced marked regression of tumor growth. Moreover, dual inhibition of HGF and VEGF by neutralizing antibodies combined with gefitinib also markedly regressed tumor growth. These results indicate the therapeutic rationale of dual targeting of HGF-Met and VEGF-VEGF receptor 2 for overcoming HGF-induced EGFR-TKI resistance in EGFR mutant lung cancer.

MiR-497 modulates multidrug resistance of human cancer cell lines by targeting BCL2

MicroRNAs (miRNAs) are short non-coding RNA molecules, which posttranscriptionally regulate genes expression and play crucial roles in diverse biological processes, such as development, differentiation, apoptosis, and proliferation. Here, we investigated the possible role of miRNAs in the development of multidrug resistance (MDR) in human gastric and lung cancer cell lines. We found that miR-497 was downregulated in both multidrug-resistant human gastric cancer cell line SGC7901/vincristine (VCR) and multidrug-resistant human lung cancer cell line A549/cisplatin (CDDP) and the downregulation of miR-497 was concurrent with the upregulation of BCL2 protein, compared with the parental SGC7901 and A549 cell lines, respectively. In vitro drug sensitivity assay demonstrated that overexpression of miR-497 sensitized SGC7901/VCR and A549/CDDP cells to anticancer drugs, respectively. The luciferase activity of BCL2 3'-untranslated region-based reporter constructed in SGC7901/VCR and A549/CDDP cells suggested that BCL2 was the direct target gene of miR-497. Enforced miR-497 expression reduced BCL2 protein level and sensitized SGC7901/VCR and A549/CDDP cells to VCR-induced and CDDP-induced apoptosis, respectively. Taken together, our findings first suggested that has-miR-497 could play a role in both gastric and lung cancer cell lines at least in part by modulation of apoptosis via targeting BCL2.

MiR‐181b modulates multidrug resistance by targeting BCL2 in human cancer cell lines

MicroRNAs (miRNAs) are short noncoding RNA molecules, which posttranscriptionally regulate genes expression and play crucial roles in diverse biological processes, such as development, differentiation, apoptosis and proliferation. Here, we investigated the possible role of miRNAs in the development of multidrug resistance (MDR) in human gastric and lung cancer cell lines. We found that miR-181b was downregulated in both multidrug-resistant human gastric cancer cell line SGC7901/vincristine (VCR) and multidrug-resistant human lung cancer cell line A549/cisplatin (CDDP), and the downregulation of miR-181b in SGC7901/VCR and A549/CDDP cells was concurrent with the upregulation of BCL2 protein, compared with the parental SGC7901 and A549 cell lines, respectively. In vitro drug sensitivity assay demonstrated that overexpression of miR-181b sensitized SGC7901/VCR and A549/CDDP cells to anticancer drugs, respectively. The luciferase activity of a BCL2 3'-untranslated region-based reporter construct in SGC7901/VCR and A549/CDDP cells suggests that a new target site in the 3'UTR of BCL2 of the mature miR-181s (miR-181a, miR-181b, miR-181c and miR-181d) was found. Enforced miR-181b expression reduced BCL2 protein level and sensitized SGC7901/VCR and A549/CDDP cells to VCR-induced and CDDP-induced apoptosis, respectively. Taken together, our findings suggest that miR-181b could play a role in the development of MDR in both gastric and lung cancer cell lines, at least in part, by modulation of apoptosis via targeting BCL2.

Resveratrol down-regulates survivin and induces apoptosis in human multidrug-resistant SPC-A-1/CDDP cells

We studied the effect of resveratrol treatment on multidrug-resistant human non-small cell lung cancer cells. Human multidrug-resistant SPC-A-1/CDDP cells were treated with resveratrol at a concentration of 25, 50, or 100 microM in in vitro studies and nude mice were implanted with multidrug-resistant SPC-A-1/and fed a special diet that included resveratrol at a dose of either 1 g/kg/day or 3 g/kg/day in in vivo studies. No adverse toxicological effects of resveratrol treatment were observed. The rate of cell proliferation, apoptosis ratio, cell cycle phase distribution, IC50 values of cisplatin, gefitinib, and paclitaxel, implanted tumour volume, and expression of survivin in resveratrol-treated and control mice were then determined. Resveratrol significantly inhibited the proliferation of SPC-A-1/CDDP cells, induced apoptosis, arrested the cell cycle phase between G0-G1 and S phase or at the G2/M phase, decreased the IC50 values of multiple chemotherapeutic drugs, and showed anti-tumour effects in nude mice that had been implanted with SPC-A-1/CDDP cells. In additional, resveratrol affected the proliferation of SPC-A-1/CDDP cells in a dose- and time-dependent manner. Expression of survivin in SPC-A-1/CDDP cells decreased after they were treated with all concentrations of resveratrol and resveratrol was also found to have a dose-dependent effect on survivin expression. Resveratrol can induce apoptosis in multidrug-resistant human NSCLC SPC-A-1/CDDP cells by down-regulating the expression of survivin.

Enhancement of the efficacy of chemotherapy for lung cancer by simultaneous suppression of multidrug resistance and antiapoptotic cellular defense: novel multicomponent delivery system.

The efficacy of chemotherapy of lung cancer is limited by the development of resistance in cancer cells during treatment. In most lung cancers, this resistance is associated with the overexpression of (a) multidrug resistance-associated protein (MRP) responsible for drug efflux from the cancer cells (pump resistance) and (b) BCL2 protein that activates antiapoptotic cellular defense (nonpump resistance). A novel liposomal proapoptotic anticancer drug delivery system was developed to enhance anticancer efficacy of the well-established drug doxorubicin (DOX). This multicomponent drug delivery system was tested on multidrug-sensitive and -resistant human small-cell lung cancer cells. The drug delivery system includes four components: (a) liposome as a carrier, (b) DOX as an inductor of apoptosis, (c) antisense oligonucleotides (ASOs) targeted to MRP1 mRNA as a suppressor of pump resistance, and (d) ASOs targeted to BCL2 mRNA as a suppressor of nonpump resistance. Intracellular internalization of ASOs and DOX; the influence of the proposed system on the expression of genes and proteins involved in the multidrug resistance, cytotoxicity, and apoptosis induction and antiapoptotic defense; and the activity of caspases were studied. It was found that the proposed liposomal delivery system successfully delivered ASOs and DOX to cell nuclei, inhibited MRP1 and BCL2 protein synthesis, and substantially increased the anticancer action of DOX by stimulating the caspase-dependent pathway of apoptosis in multidrug-resistant human lung cancer cells.

Immunological circumvention of multiple organ metastases of multidrug resistant human small cell lung cancer cells by mouse-human chimeric anti-ganglioside GM2 antibody KM966.

serum against SBC-3/DOX cells to a similar extent compared with parental SBC-3 cells. Pretreatment of human effector cells with various cytokines induced further enhancement of the KM966-dependent ADCC against SBC-3/DOX cells. Intravenous injection of SBC-3 or SBC-3/DOX cells into natural killer (NK) cell-depleted severe combined immunodeficient (SCID) mice developed metastases in multiple organs (liver, kidneys and lymph nodes). Interestingly, SBC-3/DOX cells produced metastases more rapidly than SBC-3 cells, suggesting more aggressive phenotype of SBC-3/DOX cells than their parental cells in vivo. Systemic treatment with KM966, given on days 2 and 7, drastically inhibited the formation of multiple-organ metastases produced by both SBC-3 and SBC-3/DOX cells, indicating that KM966 can eradicate metastasis by SCLC cells irrespective of MDR phenotype. These findings suggest that the mouse-human chimeric KM966 targets the GM2 antigen, and might be useful for the immunological circumvention of multiple-organ metastases of refractory SCLC.

Combined therapy with anti-P-glycoprotein antibody and macrophage colony-stimulating factor gene transduction for multiorgan metastases of multidrug-resistant human small cell lung cancer in NK cell-depleted SCID mice.

Our aim was to determine the antimetastatic potential of anti-P-glycoprotein (P-gp) antibodies (Abs) against multidrug-resistant (MDR) human small cell lung cancer (SCLC) cells expressing P-gp. Human SCLC cells H69 (P-gp negative) and its etoposide-resistant variant H69/YP (P-gp positive) were used. H69 and H69/VP cells injected i.v. metastasized to the liver, kidneys and systemic lymph nodes of NK cell-depleted severe combined immunodeficient (SCID) mice. H69/VP cells, but not H69 cells, were resistant to treatments with vindesine. Treatment with mouse-human chimeric anti-P-gp Ab (MH162) and its mouse counterpart (MRK-16) reduced metastasis of H69/VP cells in various organs and prolonged the survival of tumor-bearing mice, although they were less effective if injected at late times (after 28 days). Treatment with another mouse anti-Pgp Ab, MRK-17, was effective only against liver metastasis. MH162 and MRK-16 efficiently induced Ab-dependent cellular cytotoxicity (ADCC) by peritoneal macrophages against H69/VP cells in vitro, but MRK-17 was less effective, in accordance with their in vivo antimetastatic potential. Gene transfection of macrophage colony-stimulating factor (M-CSF) into H69/VP cells to augment macrophage-mediated ADCC resulted in inhibition of metastasis to the liver and lymph nodes, but not kidneys. Combined treatment with a low dose of MRK-16 completely cured metastasis of M-CSF transfectant, but not of the mock transfectant. Our findings suggest that while anti-P-gp Abs had antimetastatic potential against SCLC cells expressing P-gp, combined treatment with M-CSF gene transduction to augment the therapeutic efficacy of anti-P-gp Abs may be beneficial for eradicating metastatic MDR SCLC in humans.

Monocyte chemoattractant protein-1 gene modification of multidrug-resistant human lung cancer enhances antimetastatic effect of therapy with anti-P-glycoprotein antibody in SCID mice.

Distant metastases and multidrug resistance are critical problems in the therapy of human small cell lung cancer (SCLC). In this study, we investigated whether transduction of the monocyte chemoattractant protein-1 (MCP-1) gene into multidrug-resistant (MDR) human lung cancer cells affected the formation of metastases or their inhibition by the anti-P-glycoprotein (P-gp) monoclonal antibody (MAb) MRK16. MDR human SCLC (H69/VP) cells were transduced with the human MCP-1 gene inserted into the expression vector BCMGSNeo. MCP-1 gene transduction had no effect on drug sensitivity, the expression of surface antigens or the in vitro proliferation of H69/VP cells. Using the metastatic model of NK cell-depleted SCID mice, H69/VP cells transduced with the MCP-1 gene were inoculated intravenously (i.v.) and formed metastatic colonies in the liver, kidneys and lymph nodes, similar to those formed by parent or mock-transduced cells. However, systemic treatment of the mice with MRK16 reduced the metastases of H69/VP cells in the liver, kidneys and lymph nodes, and was significantly more effective in inhibiting the metastases of MCP-1 producing H69/VP than those of mock-transduced cells. MCP-1 gene transduction significantly prolonged the survival of tumor-bearing mice treated with MRK16. Our findings suggest that local production of MCP-1 in the tumor site increases the anti-P-gp antibody-dependent cell-mediated cytotoxicity, and the MCP-1 gene-induced modification of MDR human SCLC cells thereby enhances the antimetastatic effect of therapy with anti-P-gp antibody. Thus, the accumulation of effector cells in the tumor site is a very important factor in the therapy using the anti-P-gp antibody.

Circumvention of multidrug resistance by a quinoline derivative, MS-209, in multidrug-resistant human small-cell lung cancer cells and its synergistic interaction with cyclosporin A or verapamil.

To develop a clinically useful approach to circumvent P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) in MDR human small-cell lung cancer (SCLC), we examined the ability of a novel quinoline compound, MS-209, to reverse MDR by inhibition of P-gp function in combination with other MDR-reversing drugs using a cytotoxicity assay. We established MDR human SCLC cells by culture in medium with gradually increasing concentrations of adriamycin (ADM). Compared with the parental human SCLC cells, SBC-3, the MDR variant SBC-3 cells obtained (SBC-3/ADM) were highly resistant to various chemotherapeutic agents due to P-gp expression. MS-209 reversed the resistance to ADM and vincristine (VCR) of SBC-3/ADM and H69/VP cells in a dose-dependent manner. Moreover, MS-209 in combination with cyclosporin A (CsA) or verapamil (VER) synergistically enhanced the antitumor effects of ADM and VCR on SBC-3/ADM cells. MS-209 restored ADM incorporation and this effect was enhanced by CsA and VER, suggesting that these synergistic effects were due to competitive inhibition of P-gp function. MS-209 in combination with CsA or VER might increase the efficacy of these chemotherapeutic agents against MDR human SCLC cells.

45] Transport function and substrate specificity of multidrug resistance protein

Publisher Summary This chapter describes the multidrug resistance protein (MRP1) that has been cloned and sequenced from multidrug-resistant human lung cancer cells and identified as an integral membrane glycoprotein belonging to the superfamily of adenosine triphosphate-binding cassette (ABC) transporters. Primary active unidirectional adenosine triphosphate (ATP)-dependent transport of amphiphilic anions—in particular, of conjugates of lipophilic substances with glutathione, glucuronate, or sulfate, are the recognized functions of MRP1. An isoform of MRP1 with a related sequence and a similar function has been cloned from human and rat and localized predominantly to the hepatocyte canalicular membrane. This isoform is termed “MRP2” or “canalicular MRP” (cMRP) or “canalicular multispecific organic anion transporter” (cMOAT). Canalicular (apical) MRP is deficient in human Dubin–Johnson syndrome and in two mutant rat strains lacking the ATP-dependent transport of anionic conjugates across the hepatocyte canalicular membrane.

Combined therapy of p53-wt and drug in an orthotopic multidrug-resistant human lung cancer model

Balb/c nu/nu mice were inoculated intratracheally with multidrug-resistant human lung cancer cells GLK containing p53 mutation at codon 245 and treated with intratracheal instillation of p53-wt retroviral vector (pDOR53W) to increase cell chemosensitivity, and then with intraperitoneal injection of doxorubicin. 30 d after tumor cell inoculation, 75% of the control mice showed macroscopic tumors in the lung. Sole pDOR53W suppressed GLK tumor formation in 68% of mice; sole doxorubicin 33.3%, but the combination of pDOR53W and doxorubicin 88.9 %. The exogenous p53 sequence was detected and confirmed in the tumor that grew after treatment with pDOR53W retroviral vector by PCR and Southern blot hybridization with p53 cDNA. These results suggested that direct administration of a retroviral vector expressing p53-wt combined with treatment of anticancer agent was an effective therapeutic method for multidrug-resistant human lung cancer.

Combined therapy of multidrug-resistant human lung cancer with anti-P-glycoprotein antibody and monocyte chemoattractant protein-1 gene transduction: the possibility of immunological overcoming of multidrug resistance.

We determined whether transduction of the monocyte chemoattractant protein-1 (MCP-1) gene into MDR human lung cancer cells affected their tumorigenicity and sensitivity to antibody-dependent cellular cytotoxicity (ADCC) reaction mediated by the anti-P-glycoprotein (P-gp) monoclonal antibody MRK16. The human MCP-1 gene inserted into an expression vector (BCMGSNeo) was transfected into MDR human small-cell lung cancer (H69/VP) cells. Monocyte chemotactic activity was found in culture supernatants collected from MCP-1-transfected H69/VP cells, but not in supernatants of parent and mock-transfected cells. In an in vitro experiment, recombinant MCP-1 did not affect monocyte-mediated ADCC against H69/VP cells when added to the monocyte culture in either the activation or the effector phase at sufficient concentrations to attract and activate monocytes. Tumorigenicity and growth rates of MCP-1-producing H69/VP cells in nude mice were similar to those of parental cells and mock-transfected cells. However, systemic treatment with MRK16 was more effective in inhibiting the formation of tumors by MCP-1-gene-transfected cells than by mock-transfected cells. Systemic treatment with MRK16 also inhibited the growth of a mixture (1:1) of MCP-1-producing cells and mock-transfected cells. These results suggest that combination therapy with MRK16 and MCP-1 gene transduction may be a useful immunological strategy to inhibit the growth of human MDR cancer cells expressing P-gp.

Clinical Significance of Multi-Drug Resistance Associated Protein and P-Glycoprotein in Patients with Bladder Cancer

The clinical significance of multi-drug resistant proteins, such as multi-drug resistance associated protein and P-glycoprotein, in terms of prognostic value was determined in patients with bladder cancer. The expression of multi-drug resistance associated protein and P-glycoprotein was investigated immunohistochemically before and after chemotherapy. The relationship between expression of these multi-drug resistant proteins and clinical outcome assessed by tumor recurrence rate, cystectomy rate and 5-year survival rate was also investigated in 33 patients with bladder cancer. Before chemotherapy multi-drug resistance associated protein expression was observed in 1 of 28 patients (4%) while P-glycoprotein expression was observed in 22 of 33 (67%). Multi-drug resistance associated protein induction by chemotherapy was observed in 6 of 28 patients (21%), whereas P-glycoprotein induction was noted in 4 (14%). Multi-drug resistance associated protein in this disease is induced more frequently by high dose (more than 300 mg.) than low dose (less than 300 mg.) anthracyclines (p < 0.01). Immunohistochemical analysis also revealed co-expression of multi-drug resistance associated protein and P-glycoprotein in 5 of 28 patients (18%) after chemotherapy. However, there was no significant correlation between positive P-glycoprotein expression before chemotherapy and clinical outcome. Multi-drug resistance associated protein as well as P-glycoprotein mediated multi-drug resistance may be induced after chemotherapy for bladder tumors. However, the presence of P-glycoprotein before chemotherapy does not predict clinical outcome in patients with bladder cancer.

Chemotherapy of multidrug-resistant human lung cancer combined with an MDR1 ribozyme retroviral vector in an orthotopic model

Chemotherapy of multidrug-resistant human lung cancer combined with an MDR1 ribozyme retroviral vector in an orthotopic model

Reversal of drug resistance of multidrug-resistant human lung cancer cells by an MDR1 ribozyme

MALIGNANT tumor is very harmful to human health, and the mortality is very high. About 50% of the patients with malignancy can be operated on, and the other 50% patients have to be treated with chemotherapy. Because tumors are mostly chemoresistant, chemotherapy for these patients often has no effect. The overexpression of MDR1 gene is very common in hu man malignant tumors, about 50% in previously untreated patients and more than 50% in previously treated patients for whom the tumor is resistant to the previous sensitive anticancer....

Reversal of drug resistance in multidrug-resistant human lung cancer cells by MRP antisense RNA mediated by retrovirus

DRUG resistance of tumor is a very common phenomenon in clinical tumor treatment. Most patients with lung cancers, one of the most common malignant tumors in China, have no response to chemotherapy, so it is very important to study the resistant biology of lung cancer for treatment. The rate of drug sensitivity in non-small cell lung cancer (NSCLC) is lower than in small cell lung cancer (SCLC). The drug resistance, besides the effects of MDRl genet'] and GST-X'~], is also closely correlated with the effect of another novel gene MRP (multidrug resistance-related gene)[31. In the previous study on a doxorubicin-selected human NSCLC cell line, GAOK, we found that MDRl gene overexpressed and MDRl antisense RNA mediated by retrovirus could not completely reverse the phenotype of multidrug resistance['], and MRP gene and its coding product Mrp (multidrug resistance protein) also overexpressed. In the present study, in order to understand the effect of MRP in GAOK cells and possibility of reversing the multidrug resistance, we introduced MRP antisense RNA mediated by retrovirus into GAOK cells, and observed its expression and the change of multidrug resistance.